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'8') (Obsoleted by RFC 8126) Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 NFSv4 W. Adamson 3 Internet-Draft NetApp 4 Intended status: Standards Track N. Williams 5 Expires: August 7, 2014 Cryptonector 6 February 03, 2014 8 Remote Procedure Call (RPC) Security Version 3 9 draft-ietf-nfsv4-rpcsec-gssv3-07.txt 11 Abstract 13 This document specifies version 3 of the Remote Procedure Call (RPC) 14 security protocol (RPCSEC_GSS). This protocol provides for compound 15 authentication of client hosts and users to server (constructed by 16 generic composition), security label assertions for multi-level and 17 type enforcement, structured privilege assertions, and channel 18 bindings. 20 Requirements Language 22 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 23 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 24 document are to be interpreted as described in RFC 2119 [1]. 26 Status of this Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on August 7, 2014. 43 Copyright Notice 45 Copyright (c) 2014 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction and Motivation . . . . . . . . . . . . . . . . . 3 61 2. The RPCSEC_GSSv3 Protocol . . . . . . . . . . . . . . . . . . 4 62 2.1. Compatibility with RPCSEC_GSSv2 . . . . . . . . . . . . . 5 63 2.2. New REPLY verifier . . . . . . . . . . . . . . . . . . . . 5 64 2.3. New Version Number . . . . . . . . . . . . . . . . . . . . 5 65 2.4. New Control Procedures . . . . . . . . . . . . . . . . . . 7 66 2.4.1. New Control Procedure - RPCSEC_GSS_CREATE . . . . . . 8 67 2.4.2. New Control Procedure - RPCSEC_GSS_LIST . . . . . . . 14 68 2.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 15 69 2.6. New auth_stat Values . . . . . . . . . . . . . . . . . . . 15 70 3. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 16 71 4. Operational Recommendation for Deployment . . . . . . . . . . 16 72 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 73 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 74 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 75 7.1. Normative References . . . . . . . . . . . . . . . . . . . 17 76 7.2. Informative References . . . . . . . . . . . . . . . . . . 18 77 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 18 78 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 19 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 81 1. Introduction and Motivation 83 The original RPCSEC_GSS protocol [2] provided for authentication of 84 RPC clients and servers to each other using the Generic Security 85 Services Application Programming Interface (GSS-API) [3]. The second 86 version of RPCSEC_GSS [4] added support for channel bindings [5]. 88 We find that GSS-API mechanisms are insufficient for communicating 89 certain aspects of authority to a server. The GSS-API and its 90 mechanisms certainly could be extended to address this shortcoming, 91 but it seems be far simpler to address it at the application layer, 92 namely, in this case, RPCSEC_GSS. 94 The motivation for RPCSEC_GSSv3 is to add support for labeled 95 security and server-side copy for NFSv4. 97 Labeled NFS (see Section 8 of [6]) uses the subject label provided by 98 the client via the RPCSEC_GSSv3 layer to enforce MAC access to 99 objects owned by the server to enable server guest mode or full mode 100 labeled NFS. 102 A traditional inter-server file copy entails the user gaining access 103 to a file on the source, reading it, and writing it to a file on the 104 destination. In secure NFSv4 inter-server server-side copy (see 105 Section 3.4.1 of [6]), the user first secures access to both source 106 and destination files, and then uses RPCSEC_GSSv3 compound 107 authentication and structured privileges to authorize the destination 108 to copy the file from the source on behalf of the user. 110 We therefore describe RPCSEC_GSS version 3 (RPCSEC_GSSv3). 111 RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [4], except that the 112 following assertions of authority have been added. 114 o Security labels for multi-level, type enforcement, and other 115 labeled security models. See [9], [10], [11], [6] and [12]. 117 o Application-specific structured privileges. For an example see 118 server-side copy [6]. 120 o Compound authentication of the client host and user to the server 121 done by binding two RPCSEC_GSS handles. For an example see 122 server-side copy [6]. 124 o Simplified channel binding. 126 Assertions of labels and privileges are evaluated by the server, 127 which may then map the asserted values to other values, all according 128 to server-side policy. 130 We add an option for enumerating server supported label format 131 specifiers (LFS). The LFS and Label Format Registry are described in 132 detail in [13]. 134 This document contains the External Data Representation (XDR) ([7]) 135 definitions for the RPCSEC_GSSv3 protocol. The XDR description is 136 provided in this document in a way that makes it simple for the 137 reader to extract into ready to compile form. The reader can feed 138 this document in the following shell script to produce the machine 139 readable XDR description of RPCSEC_GSSv3: 141 143 #!/bin/sh 144 grep "^ *///" | sed 's?^ */// ??' | sed 's?^ *///$??' 146 148 I.e. if the above script is stored in a file called "extract.sh", and 149 this document is in a file called "spec.txt", then the reader can do: 151 153 sh extract.sh < spec.txt > rpcsec_gss_v3.x 155 157 The effect of the script is to remove leading white space from each 158 line, plus a sentinel sequence of "///". 160 2. The RPCSEC_GSSv3 Protocol 162 RPCSEC_GSSv3 is the same as RPCSEC_GSSv2 [4], except that support for 163 assertions has been added. The entire RPCSEC_GSSv3 protocol is not 164 presented. Instead the differences between RPCSEC_GSSv3 and 165 RPCSEC_GSSv2 are shown. 167 RPCSEC_GSSv3 is patterned as follows: 169 o A client uses an existing RPCSEC_GSSv3 context handle to protect 170 RPCSEC_GSSv3 exchanges, this will be termed the "parent" handle. 171 [[Comment.1: CAN A CHILD handle be used as a parent? --AA]] 173 o The server issues a "child" RPCSEC_GSSv3 handle in the 174 RPCSEC_GSS_CREATE response which uses the underlying GSS-API 175 security context of the parent handle in all subsequent exchanges 176 that uses the child handle. 178 2.1. Compatibility with RPCSEC_GSSv2 180 The functionality of RPCSEC_GSSv2 [4] is fully supported by 181 RPCSEC_GSSv3. 183 2.2. New REPLY verifier 185 The RPCSEC_GSSv3 child handle uses the same GSS context as the parent 186 handle. Since a child and parent RPCSEC_GSSv3 handle could have the 187 same RPCSEC_GSS sequence numbers, and the verifier of RPCSEC_GSS 188 replies computes a MIC on just the sequence number, this provides 189 opportunities for man in the middle attacks. 191 This is easily addressed: RPCSEC_GSS version 3 MUST change the 192 verifier of the reply to compute the verifier using the exact same 193 input as that is used for verifier of the request, except for the 194 mtype change from CALL to REPLY: 196 unsigned int xid; 197 msg_type mtype; /* set to REPLY */ 198 unsigned int rpcvers; 199 unsigned int prog; 200 unsigned int vers; 201 unsigned int proc; 202 opaque_auth cred; /* captures the RPCSEC_GSS handle */ 204 2.3. New Version Number 206 208 /// /* 209 /// * Copyright (c) 2013 IETF Trust and the persons 210 /// * identified as the document authors. All rights 211 /// * reserved. 212 /// * 213 /// * The document authors are identified in [RFC2203], 214 /// * [RFC5403], and [RFCxxxx]. 215 /// * 216 /// * Redistribution and use in source and binary forms, 217 /// * with or without modification, are permitted 218 /// * provided that the following conditions are met: 219 /// * 220 /// * o Redistributions of source code must retain the above 221 /// * copyright notice, this list of conditions and the 222 /// * following disclaimer. 223 /// * 224 /// * o Redistributions in binary form must reproduce the 225 /// * above copyright notice, this list of 226 /// * conditions and the following disclaimer in 227 /// * the documentation and/or other materials 228 /// * provided with the distribution. 229 /// * 230 /// * o Neither the name of Internet Society, IETF or IETF 231 /// * Trust, nor the names of specific contributors, may be 232 /// * used to endorse or promote products derived from this 233 /// * software without specific prior written permission. 234 /// * 235 /// * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 236 /// * AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED 237 /// * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 238 /// * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 239 /// * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO 240 /// * EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 241 /// * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 242 /// * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 243 /// * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 244 /// * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 245 /// * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 246 /// * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 247 /// * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 248 /// * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 249 /// * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 250 /// */ 251 /// 252 /// /* 253 /// * This code was derived from [RFC2203]. Please 254 /// * reproduce this note if possible. 255 /// */ 256 /// 257 /// enum rpc_gss_service_t { 258 /// /* Note: the enumerated value for 0 is reserved. */ 259 /// rpc_gss_svc_none = 1, 260 /// rpc_gss_svc_integrity = 2, 261 /// rpc_gss_svc_privacy = 3, 262 /// rpc_gss_svc_channel_prot = 4 263 /// }; 264 /// 265 /// enum rpc_gss_proc_t { 266 /// RPCSEC_GSS_DATA = 0, 267 /// RPCSEC_GSS_INIT = 1, 268 /// RPCSEC_GSS_CONTINUE_INIT = 2, 269 /// RPCSEC_GSS_DESTROY = 3, 270 /// RPCSEC_GSS_BIND_CHANNEL = 4, /* not used */ 271 /// RPCSEC_GSS_CREATE = 5, /* new */ 272 /// RPCSEC_GSS_LIST = 6 /* new */ 273 /// }; 274 /// 275 /// struct rpc_gss_cred_vers_1_t { 276 /// rpc_gss_proc_t gss_proc; /* control procedure */ 277 /// unsigned int seq_num; /* sequence number */ 278 /// rpc_gss_service_t service; /* service used */ 279 /// opaque handle<>; /* context handle */ 280 /// }; 281 /// 282 /// const RPCSEC_GSS_VERS_1 = 1; 283 /// const RPCSEC_GSS_VERS_2 = 2; 284 /// const RPCSEC_GSS_VERS_3 = 3; /* new */ 285 /// 286 /// union rpc_gss_cred_t switch (unsigned int rgc_version) { 287 /// case RPCSEC_GSS_VERS_1: 288 /// case RPCSEC_GSS_VERS_2: 289 /// case RPCSEC_GSS_VERS_3: /* new */ 290 /// rpc_gss_cred_vers_1_t rgc_cred_v1; 291 /// }; 292 /// 294 296 As seen above, the RPCSEC_GSSv3 credential has the same format as the 297 RPCSEC_GSSv1 [2] and RPCSEC_GSSv2 [4] credential. Setting the 298 rgc_version field to 3 indicates that the initiator and target 299 support the new RPCSEC_GSSv3 control procedures. 301 2.4. New Control Procedures 303 There are two new RPCSEC_GSSv3 control procedures: RPCSEC_GSS_CREATE, 304 RPCSEC_GSS_LIST. 306 The RPCSEC_GSS_CREATE procedure binds any combination of assertions: 307 compound authentication, labels, structured privileges, or channel 308 bindings to a new RPCSEC_GSSv3 context returned in the 309 rgss3_create_res rcr_handle field. 311 The RPCSEC_GSS_LIST procedure queries the target for supported 312 assertions. 314 RPCSEC_GSS version 3 control messages are similar to the RPCSEC_GSS 315 version 1 and version2 RPCSEC_GSS_DESTROY control message (see 316 section 5.4 [2]) in that the sequence number in the request must be 317 valid, and the header checksum in the verifier must be valid. As in 318 RPCSEC_GSS version 1 and version 2, the RPCSEC_GSSv version 3 control 319 messages may contain call data following the verifier in the body of 320 the NULLPROC procedure. In other words, they look a lot like an 321 RPCSEC_GSS data message with the header procedure set to NULLPROC. 323 The client MUST use one of the following security services to protect 324 the RPCSEC_GSS_CREATE or RPCSEC_GSS_LIST control message: 326 o rpc_gss_svc_channel_prot (see RPCSEC_GSSv2 [4]) 328 o rpc_gss_svc_integrity 330 o rpc_gss_svc_privacy 332 Specifically the client MUST NOT use rpc_gss_svc_none. 334 2.4.1. New Control Procedure - RPCSEC_GSS_CREATE 336 338 /// struct rgss3_create_args { 339 /// rgss3_gss_binding *rca_comp_auth; 340 /// rgss3_chan_binding *rca_chan_bind_mic; 341 /// rgss3_assertion rca_assertions<>; 342 /// }; 343 /// 344 /// struct rgss3_create_res { 345 /// opaque rcr_handle<>; 346 /// rgss3_gss_binding *rcr_comp_auth; 347 /// rgss3_chan_binding *rcr_chan_bind_mic; 348 /// rgss3_assertion rcr_assertions<>; 349 /// }; 350 /// 351 /// enum rgss3_assertion_type { 352 /// LABEL = 0, 353 /// PRIVS = 1 354 /// }; 355 /// 356 /// union rgss3_assertion_u 357 /// switch (rgss3_assertion_type atype) { 358 /// case LABEL: 359 /// rgss3_label rau_label; 360 /// case PRIVS: 361 /// rgss3_privs rau_privs; 362 /// default: 363 /// opaque rau_ext<>; 364 /// }; 365 /// 366 /// struct rgss3_assertion { 367 /// bool ra_critical; 368 /// rgss3_assertion_u ra_assertion; 369 /// }; 370 /// 372 374 The call data for an RPCSEC_GSS_CREATE request consists of an 375 rgss3_create_args which binds one or more items of several kinds to 376 the returned rcr_handle RPCSEC_GSSv3 context handle called the 377 "child" handle: 379 o Compound authentication: another RPCSEC_GSS context handle 381 o Authorization assertions: labels and or privileges 383 o A channel binding 385 The reply to this message consists of either an error or an 386 rgss3_create_res structure. 388 Upon successful RPCSEC_GSS_CREATE, both the client and the server 389 SHOULD associate the resultant child rcr_handle context handle with 390 the parent context handle in their GSS context caches so as to be 391 able to reference the parent context given the child context handle. 393 RPCSEC_GSSv3 child handles MUST be destroyed upon the destruction of 394 the associated parent handle. 396 Server implementation and policy MAY result in labels, privileges, 397 and identities being mapped to concepts and values that are local to 398 the server. Server policies should take into account the identity of 399 the client and/or user as authenticated via the GSS-API. 401 2.4.1.1. Compound Authentication 403 405 /// 406 /// struct rgss3_gss_binding { 407 /// opaque rgb_handle<>; /* inner handle */ 408 /// opaque rgb_nonce<>; 409 /// opaque rgb_nounc_mic<>; 410 /// }; 411 /// 413 415 RPCSEC_GSSv3 clients MAY assert a compound authentication of the 416 client host and a user. This is done by including an assertion of 417 type rgss3_gss_binding in the RPCSEC_GSS_CREATE rgss3_create_args 418 call data. In addition to the parent handle (Section 2), the 419 compound authentication rgss3_gss_binding call data has an RPCSEC_GSS 420 version 3 handle referenced via the rgb_handle field termed the 421 "inner" handle. A nonce and a MIC of that nounce created using the 422 GSS-API security context associated with the inner handle is also 423 provided. 425 The target verifies the compounding by verifying the rgb_nouce_mic. 426 On a successful reply, the rgss3_gss_binding field in the 427 rgss3_create_res reply uses the parent RPCSEC_GSSv3 context as the 428 rgb_handle, the same rgb_nounce as was sent in the call data with the 429 rgb_nounce_mic created using the GSS-API security context associate 430 with the parent handle. Verification of the rbg_nounce_mic by the 431 initiator demonstrates that the target agrees to the compounding. On 432 failure, the rgss3_gss_binding field is not sent. (rgss3_gss_binding 433 is an optional field) 435 This feature is needed, for example, when a client wishes to use 436 authority assertions that the server may only grant if a user and a 437 client are authenticated together to the server. Thus a server may 438 refuse to grant requested authority to a user acting alone (e.g., via 439 an unprivileged user-space program), or to a client acting alone 440 (e.g. when a client is acting on behalf of a user) but may grant 441 requested authority to a client acting on behalf of a user if the 442 server identifies the user and trusts the client. 444 It is assumed that an unprivileged user-space program would not have 445 access to client host credentials needed to establish a GSS-API 446 security context authenticating the client to the server, therefore 447 an unprivileged user-space program could not create an RPCSEC_GSSv3 448 RPCSEC_GSS_CREATE message that successfully binds a client and a user 449 security context. 451 Clients using RPCSEC_GSSv3 compound authentication MUST use an 452 RPCSEC_GSSv3 context handle that corresponds to a GSS-API security 453 context that authenticates the client host for the outer handle. The 454 inner context handle it SHOULD use a context handle to authenticate a 455 user. The reverse (outer handle authenticates user, inner 456 authenticates client) MUST NOT be used. Other compounds might 457 eventually make sense. 459 An inner RPCSEC_GSSv3 context handle that is bound to an outer 460 RPCSEC_GSS context MUST be treated by servers as authenticating the 461 GSS-API initiator principal authenticated by the inner context 462 handle's GSS- API security context. This principal may be mapped to 463 a server-side notion of user or principal. 465 2.4.1.2. Label Assertions 467 469 /// struct rgss3_label { 470 /// rgss3_lfs rl_lfs; 471 /// opaque rl_label<>; 472 /// }; 473 /// 474 /// struct rgss3_lfs { 475 /// unsigned int rlf_lfs_id; 476 /// unsigned int rlf_pi_id; 477 /// }; 478 /// 480 482 The client discovers which labels the server supports via the 483 RPCSEC_GSS_LIST control message. 485 RPCSEC_GSSv3 clients MAY assert a server security label in some LSF 486 by binding a label assertion to the RPCSEC_GSSv3 context handle. 487 This is done by including an assertion of type rgss3_label in the 488 RPCSEC_GSS_CREATE rgss3_create_args rca_assertions call data. 490 The labels that are accepted by the target and bound to the 491 RPCSEC_GSSv3 context will be enumerated in the rcr_assertions field 492 of the rgss3_create_res RPCSEC_GSS_CREATE reply. 494 Label encoding is specified to mirror the NFSv4.2 sec_label attribute 495 described in Section 12.2.2 of [6]. The label format specifier (LFS) 496 is an identifier used by the client to establish the syntactic format 497 of the security label and the semantic meaning of its components. 498 The policy identifier (PI) is an optional part of the definition of 499 an LFS which allows for clients and server to identify specific 500 security policies. The opaque label field of rgss3_label is 501 dependent on the MAC model to interpret and enforce. 503 Asserting a server supported label via RPCSEC_GSS_CREATE enables 504 server guest mode labels. Full mode is enabled when an 505 RPCSEC_GSS_CREATE label assertion is combined with asserting the same 506 label with the NFSv4.2 sec_label attribute. 508 [[Comment.2: Check that this Label discussion provides all the 509 required pieces to enable full mode when combined with NFSv4.2 LNFS. 510 Specifically, how does the client find out and respond if a server 511 has changed a label. --AA]] 512 If a label itself requires privacy protection (i.e., that the user 513 can assert that label is a secret) then the client MUST use the 514 rpc_gss_svc_privacy protection service for the RPCSEC_GSS_CREATE 515 request or, if the parent handle is bound to a secure channel that 516 provides privacy protection, rpc_gss_svc_channel_prot. 518 If a client wants to ensure that the server understands the asserted 519 label then it MUST set the 'critical' field of the label assertion to 520 TRUE, otherwise it MUST set it to FALSE. 522 Servers that do not support labeling MUST ignore non-critical label 523 assertions. Servers that do not support the requested LFS MUST 524 either ignore non-critical label assertions or map them to a suitable 525 label in a supported LFS. Servers that do not support labeling or do 526 not support the requested LFS MUST return an error if the label 527 request is critical. Servers that support labeling in the requested 528 LFS MAY map the requested label to different label as a result of 529 server-side policy evaluation. 531 2.4.1.3. Structured Privilege Assertions 533 535 /// 536 /// struct rgss3_privs { 537 /// string rp_name<>; /* human readable */ 538 /// opaque rp_privilege<>; 539 /// }; 541 543 A structured privilege is an RPC application defined privilege. 544 RPCSEC_GSSv3 clients MAY assert a structured privilege by binding the 545 privilege to the RPCSEC_GSSv3 context handle. This is done by 546 including an assertion of type rgss3_privs in the RPCSEC_GSS_CREATE 547 rgss3_create_args rca_assertions call data. Encoding, server 548 verification and any policies for structured privileges are described 549 by the RPC application definition. 551 A successful structured privilege assertion will be enumerated in the 552 rcr_assertions field of the rgss3_create_res RPCSEC_GSS_CREATE reply. 554 Section 3.4.1.2. "Inter-Server Copy with RPCSEC_GSSv3" of [6] shows 555 an example of structured privilege definition and use. 557 2.4.1.4. Channel Binding 559 561 /// 562 /// typedef opaque rgss3_chan_binding<>; 563 /// 565 567 RPCSEC_GSSv3 provides a different way to do channel binding than 568 RPCSEC_GSSv2 [4]. Specifically: 570 a. RPCSEC_GSSv3 builds on RPCSEC_GSSv1 by reusing existing, 571 established context handles rather than providing a different RPC 572 security flavor for establishing context handles, 574 b. channel bindings data are not hashed because the community now 575 agrees that it is the secure channel's responsibility to produce 576 channel bindings data of manageable size. 578 (a) is useful in keeping RPCSEC_GSSv3 simple in general, not just for 579 channel binding. (b) is useful in keeping RPCSEC_GSSv3 simple 580 specifically for channel binding. 582 Channel binding is accomplished as follows. The client prefixes the 583 channel bindings data octet string with the channel type as described 584 in [5], then the client calls GSS_GetMIC() to get a MIC of resulting 585 octet string, using the RPCSEC_GSSv3 context handle's GSS-API 586 security context. The MIC is then placed in the rca_chan_bind_mic 587 field of RPCSEC_GSS_CREATE arguments (rgss3_create_args). 589 If the rca_chan_bind_mic field of the arguments of a 590 RPCSEC_GSS_CREATE control message is set, then the server MUST verify 591 the client's channel binding MIC if the server supports this feature. 592 If channel binding verification succeeds then the server MUST 593 generate a new MIC of the same channel bindings and place it in the 594 rcr_chan_bind_mic field of the RPCSEC_GSS_CREATE rgss3_create_res 595 results. If channel binding verification fails or the server doesn't 596 support channel binding then the server MUST indicate this in its 597 reply by not including a rgss3_chan_binding value in rgss3_create_res 598 (rgss3_chan_binding is an optional field). 600 The client MUST verify the result's rcr_chan_bind_mic value by 601 calling GSS_VerifyMIC() with the given MIC and the channel bindings 602 data (including the channel type prefix). If client-side channel 603 binding verification fails then the client MUST call 604 RPCSEC_GSS_DESTROY. If the client requested channel binding but the 605 server did not include an rcr_chan_binding_mic field in the results, 606 then the client MAY continue to use the resulting context handle as 607 though channel binding had never been requested, otherwise (if the 608 client really wanted channel binding) it MUST call 609 RPCSEC_GSS_DESTROY. 611 As per-RPCSEC_GSSv2 [4]: 613 "Once a successful [channel binding] procedure has been performed 614 on an [RPCSEC_GSSv3] context handle, the initiator's 615 implementation may map application requests for rpc_gss_svc_none 616 and rpc_gss_svc_integrity to rpc_gss_svc_channel_prot credentials. 617 And if the secure channel has privacy enabled, requests for 618 rpc_gss_svc_privacy can also be mapped to 619 rpc_gss_svc_channel_prot." 621 Any RPCSEC_GSSv3 context handle that has been bound to a secure 622 channel in this way SHOULD be used only with the 623 rpc_gss_svc_channel_prot, and SHOULD NOT be used with 624 rpc_gss_svc_none nor rpc_gss_svc_integrity -- if the secure channel 625 does not provide privacy protection then the client MAY use 626 rpc_gss_svc_privacy where privacy protection is needed or desired. 628 2.4.2. New Control Procedure - RPCSEC_GSS_LIST 630 632 /// enum rgss3_list_item { 633 /// LABEL = 0, 634 /// PRIVS = 1 635 /// }; 636 /// 637 /// struct rgss3_list_args { 638 /// rgss3_list_item rla_list_what<>; 639 /// }; 640 /// 641 /// union rgss3_list_item_u 642 /// switch (rgss3_list_item itype) { 643 /// case LABEL: 644 /// rgss3_label rli_labels<>; 645 /// case PRIVS: 646 /// rgss3_privs rli_privs<>; 647 /// default: 648 /// opaque rli_ext<>; 649 /// }; 650 /// 651 /// typedef rgss3_list_item_u rgss3_list_res<>; 652 /// 654 656 The call data for an RPCSEC_GSS_LIST request consists of a list of 657 integers (rla_list_what<>) indicating what assertions to be listed, 658 and the reply consists of an error or the requested list. 660 [[Comment.3: What good is the rli_ext field? How should we describe 661 it's use? --AA]] 663 The result of requesting a list of rgss3_list_item LABEL is a list of 664 LFSs supported by the server. The client can then use the LFS list 665 to assert labels via the RPCSEC_GSS_CREATE label assertions. See 666 Section 2.4.1.2. 668 2.5. Extensibility 670 Assertion types may be added in the future by adding arms to the 671 'rgss3_assertion_u' union. Every assertion has a 'critical' flag 672 that can be used to indicate criticality. Other assertion types are 673 described elsewhere and include: 675 o Client-side assertions of identity: 677 * Primary client/user identity 679 * Supplementary group memberships of the client/user, including 680 support for specifying deltas to the membership list as seen on 681 the server. 683 New control message types may be added. 685 Servers receiving unknown critical client assertions MUST return an 686 error. 688 2.6. New auth_stat Values 690 RPCSEC_GSSv3 requires the addition of several values to the auth_stat 691 enumerated type definition: 693 enum auth_stat { 694 ... 695 /* 696 * RPCSEC_GSSv3 errors 697 */ 698 RPCSEC_GSS_COMPOUND_PROBLEM = <>, 699 RPCSEC_GSS_LABEL_PROBLEM = <>, 700 RPCSEC_GSS_UNKNOWN_PRIVILEGE = <> 701 RPCSEC_GSS_UNKNOWN_MESSAGE = <> 703 }; 705 [[Comment.4: fix above into YYY. All the entries are TBD... --NW]] 706 [[Comment.5: The compound authentication problems are: can't find the 707 handle plus handle version on the target, or the MIC of the nounce 708 does not match. Both of these errors already have auth_stat entries: 709 RPCSEC_GSS_CREDPROBLEM for the first and "reply status of 710 MSG_ACCEPTED, and an acceptance status of GARBAGE_ARGS." --AA]] 712 3. Version Negotiation 714 An initiator that supports version 3 of RPCSEC_GSS simply issues an 715 RPCSEC_GSS request with the rgc_version field set to 716 RPCSEC_GSS_VERS_3. If the target does not recognize 717 RPCSEC_GSS_VERS_3, the target will return an RPC error per Section 718 5.1 of [2]. 720 The initiator MUST NOT attempt to use an RPCSEC_GSS handle returned 721 by version 3 of a target with version 1 or version 2 of the same 722 target. The initiator MUST NOT attempt to use an RPCSEC_GSS handle 723 returned by version 1 or version 2 of a target with version 3 of the 724 same target. 726 4. Operational Recommendation for Deployment 728 RPCSEC_GSSv3 is a superset of RPCSEC_GSSv2 [4] which in turn is a 729 superset of RPCSEC_GSSv1 [2], and so can be used in all situations 730 where RPCSEC_GSSv1 or RPCSEC_GSSv2 is used. RPCSEC_GSSv3 should be 731 used when the new functionality is needed. 733 5. Security Considerations 735 This entire document deals with security issues. 737 The RPCSEC_GSSv3 protocol allows for client-side assertions of data 738 that is relevant to server-side authorization decisions. These 739 assertions must be evaludated by the server in the context of whether 740 the client and/or user are authenticated, whether compound 741 authentication was used, whether the client is trusted, what ranges 742 of assertions are allowed for the client and the user (separately or 743 together), and any relevant server-side policy. 745 The security semantics of assertions carried by RPCSEC_GSSv3 are 746 application protocol-specific. 748 RPCSEC_GSSv3 supports a notion of critical assertions but there's no 749 need for peers to tell each other what assertions were granted, or 750 what they were mapped to. 752 Note that RPSEC_GSSv3 is not a complete solution for labeling: it 753 conveys the labels of actors, but not the labels of objects. RPC 754 application protocols may require extending in order to carry object 755 label information. 757 There may be interactions with NFSv4's callback security scheme and 758 NFSv4.1's GSS-API "SSV" mechanisms. Specifically, the NFSv4 callback 759 scheme requires that the server initiate GSS-API security contexts, 760 which does not work well in practice, and in the context of client- 761 side processes running as the same user but with different privileges 762 and security labels the NFSv4 callback security scheme seems 763 particularly unlikely to work well. NFSv4.1 has the server use an 764 existing, client-initiated RPCSEC_GSS context handle to protect 765 server-initiated callback RPCs. The NFSv4.1 callback security scheme 766 lacks all the problems of the NFSv4 scheme, however, it is important 767 that the server pick an appropriate RPCSEC_GSS context handle to 768 protect any callbacks. Specifically, it is important that the server 769 use RPCSEC_GSS context handles which authenticate the client to 770 protect any callbacks relating to server state initiated by RPCs 771 protected by RPCSEC_GSSv3 contexts. 773 [[Comment.6: [Add text about interaction with GSS-SSV...] --NW]] 775 [[Comment.7: AFAICS the reason to use SSV is to avoid using a client 776 machine credential which means compound authentication can not be 777 used. --AA]] 779 6. IANA Considerations 781 This section uses terms that are defined in [8]. 783 There are no IANA considerations in this document. TBDs in this 784 document will be assigned by the ONC RPC registrar (which is not 785 IANA, XXX: verify). 787 7. References 789 7.1. Normative References 791 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 792 Levels", RFC 2119, March 1997. 794 [2] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol 795 Specification", RFC 2203, September 1997. 797 [3] Linn, J., "Generic Security Service Application Program 798 Interface Version 2, Update 1", RFC 2743, January 2000. 800 [4] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February 2009. 802 [5] Williams, N., "On the Use of Channel Bindings to Secure 803 Channels", RFC 5056, November 2007. 805 [6] Haynes, T., "NFS Version 4 Minor Version 2", 806 draft-ietf-nfsv4-minorversion2-21 (Work In Progress), 807 March 2013. 809 [7] Eisler, M., "XDR: External Data Representation Standard", 810 RFC 4506, May 2006. 812 [8] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 813 Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. 815 7.2. Informative References 817 [9] "Section 46.6. Multi-Level Security (MLS) of Deployment Guide: 818 Deployment, configuration and administration of Red Hat 819 Enterprise Linux 5, Edition 6", 2011. 821 [10] Smalley, S., "The Distributed Trusted Operating System (DTOS) 822 Home Page", 823 . 825 [11] Carter, J., "Implementing SELinux Support for NFS", 826 . 828 [12] Haynes, T., "Requirements for Labeled NFS", 829 draft-ietf-nfsv4-labreqs-05 (work in progress). 831 [13] Quigley, D. and J. Lu, "Registry Specification for MAC Security 832 Label Formats", draft-quigley-label-format-registry (work in 833 progress), 2011. 835 Appendix A. Acknowledgments 836 Appendix B. RFC Editor Notes 838 [RFC Editor: please remove this section prior to publishing this 839 document as an RFC] 841 [RFC Editor: prior to publishing this document as an RFC, please 842 replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the 843 RFC number of this document] 845 Authors' Addresses 847 William A. (Andy) Adamson 848 NetApp 849 3629 Wagner Ridge Ctt 850 Ann Arbor, MI 48103 851 USA 853 Phone: +1 734 665 1204 854 Email: andros@netapp.com 856 Nico Williams 857 cryptonector.com 858 13115 Tamayo Dr 859 Austin, TX 78729 860 USA 862 Email: nico@cryptonector.com